An aneurysm is an abnormal widening or expansion of a blood vessel, such as an artery, which occurs in a localized area of the artery and is typically the result of a weakening of the arterial wall caused by disease. The expansion is usually accompanied by a collection of fluid or clotted blood in the localized area. If the aneurysm is not treated, it typically will continue to expand, and may rupture, causing dangerous internal bleeding.
The most common locations for aneurysms are in the abdominal aorta, between the renal arteries and the split of the abdominal aorta into the left and right common iliac arteries, and in the upper legs, in the common iliac adjacent the take off of the internal iliac. Other vessels can be affected as well. The aneurysms in some cases involve only a single, main artery, but in other cases, one or more secondary arteries, branching from the main artery, are also weakened by disease and abnormally expanded. Such secondary arteries include the renal arteries and the superior mesenteric artery on the abdominal aorta, and the internal iliac off the common iliac artery.
Open surgery has been used to repair aneurysms, but, at least in part due to the morbidity rates associated with open surgery, percutaneous procedures are replacing it. The aneurysm is repaired in the percutaneous procedures by placing a covered stent in the affected main artery. However, such covered stents, particularly in the case of an aneurysm affecting one or more secondary arteries, such as the renal arteries or the internal iliac, do not adequately seal the aneurysm and are prone to leakage in the area adjacent the secondary arteries.